In recent years, carbon dioxide capture and storage (CCS) technology has received attention as an effective measure for the global warming problem. For example, a carbon dioxide capturing system is investigated that captures carbon dioxide in a process exhaust gas (treatment target gas) generated from a combustion boiler and the like of a thermal power station or ironworks by using an absorption liquid.
In such a carbon dioxide capturing system, when a variation in load of the boiler or a change in supply amount of air or fuel has been generated according to a change in operation of the thermal power station or the ironworks, a carbon dioxide concentration and a gas flow rate of the supplied process exhaust gas rapidly change. However, a conventional carbon dioxide capturing system cannot deal with these rapid changes by changing process conditions of the carbon dioxide capturing system. Accordingly, the carbon dioxide capturing system becomes unstable and generates abnormal heat.
In addition, such a carbon dioxide capturing system is desirably started promptly up to a rated operation point. However, when operating conditions of the carbon dioxide capturing system are set to become highly efficient, the circulating flow rate of the absorption liquid is small and a heat quantity to be charged into a reboiler per unit time is small. Accordingly, it takes long time for the carbon dioxide capturing system to be started up.
Furthermore, the carbon dioxide capturing system for the plant which discharges a large amount of process exhaust gas holds a large amount of the absorption liquid. Accordingly, it takes long time for the absorption liquid to be circulated in the carbon dioxide capturing system. Therefore, when the operation of the carbon dioxide capturing system is in an unstable state, it takes long time to shift the unstable state to a steady state. Furthermore, when the operating conditions of the carbon dioxide capturing system are changed along with the variation in load of the combustion boiler and the like, it also takes long time to shift the operation of the carbon dioxide capturing system from the unstable state to the steady state.